There is great excitement and hopefulness regarding plasticity of the brain, especially in very young children. Yet, no one knows with certainty whether the immature brain is more or less vulnerable to or resilient from injury. To answer this question, age at injury must be isolated as an independent variable, a challenging task since there are multiple factors that determine outcome. It is anticipated that exploratory research in this area will lead to preventative strategies and rational therapeutic designs tailored to the unique attributes of the developing brain. In response to the NIH program announcement "Exploratory Grants in Pediatric Brain Disorders: Integrating the Science" we propose a pilot project to refine the methodology and determine an appropriate sample size for an adequately powered multi-centered study. The primary hypothesis is that TBI at a younger age results in higher developmental and functional outcome scores than TBI at an older age, controlling for other relevant variables. Additional hypotheses examine the predictive value of the Apolipoprotein E gene, neuron specific enolase, and protein S100B. Eighty children 3 years-of-age or younger, admitted to the hospital for traumatic brain injury, will be enrolled in a pilot study over two years with follow-up at 6 and 12 months post injury. An extensive database on demographics, pre- and in-hospital course, imaging and laboratory studies, and a detailed interview of the parent/caretaker/observer will be completed. DNA will be analyzed for APO E alleles at Duke University and two samples of blood obtained 12 hours apart will be analyzed at the University of Pittsburgh for NSE and a protein S100B. At 6 and 12 months post injury, subjects will receive detailed neurological, sensory, developmental, behavioral, and functional assessments using standardized instruments. This pilot project is an attempt to enhance our scientific knowledge in understanding the pathobiology and treatment of brain injury in infants and toddlers. It addresses explicit areas of interest in the PA: injury to the developing brain, plasticity, and outcomes of age-specific injury. This project will be far more comprehensive than previous studies of brain injury in infants and toddlers and will explore novel hypotheses regarding genetic determinants of outcome and markers of neuronal injury in young children. [unreadable] [unreadable]